1. Field of the Invention
This invention relates to novel liquid-crystalline substances and liquid crystal compositions containing the same, and more particularly it relates to chiral liquid-crystalline substances and chiral liquid crystal compositions containing the same.
2. Description of the Prior Art
As liquid crystal display elements, those of TN (twisted nematic) type display mode have currently been most broadly employed, but they are inferior to luminescent type display elements (electroluminescence, plasma display, etc.) in the aspect of response rate. Various attempts to improve the response rate have been made, but nevertheless it does not appear that a possibility of improvement to a large extent has been found. Thus, extensive research has been made on liquid crystal display devices in place of TN type display elements, based on another principle, and among these there is a display mode utilizing ferroelectric liquid crystals (N. A. Clark et al; Applied Phys. lett., 36, 899 (1980)). This mode utilizes chiral smectic C phase (hereinafter abbreviated to Sc* phase) or chiral smectic H phase (hereinafter abbreviated to SH* phase), and substances having these phases in the vicinity of room temperature have been desired as suitable ones to this mode. The present inventors have previously found certain chiral smectic compounds suitable to such an object and have applied for patents (e.g. Japanese patent application Nos. Sho 58-640/1983, Sho 58-78,594/1983, Sho 58-106,100/1983, Sho 59-18,086/1984, etc.). Applicants have further searched for various liquid crystal substances having an optically active group therein in order to find superior compounds suitable to this display mode, and have found the novel compounds of the present invention.